<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <ul>
      <li>1</li>
      <li>2</li>
      <li>3</li>
    </ul>
    <h1>标题</h1>

    <style>
      * {
        margin: 0px;
        padding: 0px;
      }
      ul {
        /* float: left; */
        /* overflow: hidden; */
        list-style: none;
        border: 5px solid #ccc;
      }
      /* ul::after {
        content: "";
        display: block;
        clear: both;
      } */
      li {
        float: left;
        width: 100px;
        height: 100px;
        margin: 10px;
        background: #345;
      }
    </style>
  </body>
</html>
